The present invention relates to an illumination device for producing light color of natural light which gives no feeling of physical disorder against artificial light by using natural light together with artificial light to thereby save energy.
Recently, variety of environmental pollutions have been generated with the development of industries, so that the environmental problems have become regarded as important. Further, the finiteness of resources has been pointed out and the movement of promoting energy saving has become extensive. Recently also with respect to an illumination source, therefore, various devices such as provision of skylights, widening of windows, etc., are employed in buildings under the consideration of using natural light as much as possible in the day time.
However, when only natural light is used, sometimes the light becomes not sufficient depending on location, or in an evening, the quantity of light becomes not insufficient. In such cases, accordingly, illumination is performed by a combination of natural light and artificial light.
Since the light color of natural light in the evening is very reddish, however, the light color of the natural light becomes so different from the light color of artificial light that the balance of light color becomes bad depending on the room, and an influence is given to the characteristics of the human sense of color to make the sense obscure to cause characters which can not be recognized. To cope with this, there has been developed no illumination device for natural light in which the light color of natural light is made to be in accord with that of artificial light while taking the difference in light color between natural light and artificial light into consideration. Accordingly, there has been caused a feeling of physical disorder in a room even if natural light is used or it has been impossible to use natural light sufficiently effectively in the evening.